Re: [PATCH] KVM: PCIPT: VT-d support

[Avi Kivity <avi@qumranet.com>]

Ben-Ami Yassour wrote:
> On Sun, 2008-07-13 at 10:34 +0300, Avi Kivity wrote:
>   
>> Muli Ben-Yehuda wrote:
>>     
>>>> On the other hand, this means that you will not be able to assign
>>>> devices unless you specified this when creating the VM; but I think
>>>> this is fair.
>>>>     
>>>>         
>>> It will be nice to support hot-plugged pass-through devices some time
>>> in the future.
>>>
>>>   
>>>       
>> And it should be easy to do too.  The question is whether we need to 
>> allocate the iommu domain up front (which would mean that a command line 
>> parameter would be needed, meaning roughly 'support pci device 
>> assignment on this guest'.  Kind of like -usb, which means 'support usb 
>> device assignment on this guest'.
>>
>>     
>
> I don't think that its that simple...
> On a single machine you can have multiple iommu units, each of which controls certain PCI slots.
> To configure the iommu for a specific device you need to configure the iommu unit that controls that device.
> This means that we need to know the bus/dev/func of the device before we create the VT-d domain.
> For hot-plug devices it means that by the time we can create the domain we already have memory slots that we need to add to the VT-d mapping.
>
>   

Thanks for the info.  Looks like we have to support both 
memslot-before-iommu and memslot-after-iommu then.

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